Chronic, nonresolving inflammation is a critical factor in the clinical progression of advanced atherosclerotic lesions. In the normal inflammatory response, resolution is mediated by several agonists, among which is the glucocorticoid-regulated protein called annexin A1. The proresolving actions of annexin A1, which are mediated through its receptor N-formyl peptide receptor 2 (FPR2/ALX), can be mimicked by an amino-terminal peptide encompassing amino acids 2–26 (Ac2-26). Collagen IV (Col IV)–targeted nanoparticles (NPs) containing Ac2-26 were evaluated for their therapeutic effect on chronic, advanced atherosclerosis in fat-fed Ldlr−/− mice. When administered to mice with preexisting lesions, Col IV–Ac2-26 NPs were targeted to lesions and led to a marked improvement in key advanced plaque properties, including an increase in the protective collagen layer overlying lesions (which was associated with a decrease in lesional collagenase activity), suppression of oxidative stress, and a decrease in plaque necrosis. In mice lacking FPR2/ALX in myeloid cells, these improvements were not seen. Thus, administration of a resolution-mediating peptide in a targeted NP activates its receptor on myeloid cells to stabilize advanced atherosclerotic lesions. These findings support the concept that defective inflammation resolution plays a role in advanced atherosclerosis, and suggest a new form of therapy.

Imbalances between proinflammatory and proresolving mediators can lead to chronic inflammatory diseases. The balance of arachidonic acid-derived mediators in leukocytes is thought to be achieved through intracellular localization of 5-lipoxygenase (5-LOX): nuclear 5-LOX favors the biosynthesis of proinflammatory leukotriene B 4 (LTB 4 ), whereas, in theory, cytoplasmic 5-LOX could favor the biosynthesis of proresolving lipoxin A 4 (LXA 4 ). This balance is shifted in favor of LXA 4 by resolvin D1 (RvD1), a specialized proresolving mediator derived from docosahexaenoic acid, but the mechanism is not known. Here we report a new pathway through which RvD1 promotes nuclear exclusion of 5-LOX and thereby suppresses LTB 4 and enhances LXA 4 in macrophages. RvD1, by activating its receptor formyl peptide receptor2/lipoxin A 4 receptor, suppresses cytosolic calcium and decreases activation of the calcium-sensitive kinase calcium-calmodulin-dependent protein kinase II (CaMKII). CaMKII inhibition suppresses activation P38 and mitogen-activated protein kinase-activated protein kinase 2 kinases, which reduces Ser271 phosphorylation of 5-LOX and shifts 5-LOX from the nucleus to the cytoplasm. As such, RvD1's ability to decrease nuclear 5-LOX and the LTB 4 :LXA 4 ratio in vitro and in vivo was mimicked by macrophages lacking CaMKII or expressing S271A-5-LOX. These findings provide mechanistic insight into how a specialized proresolving mediator from the docosahexaenoic acid pathway shifts the balance toward resolution in the arachidonic acid pathway. Knowledge of this mechanism may provide new strategies for promoting inflammation resolution in chronic inflammatory diseases.P ersistent inflammation and its failed resolution underlie the pathophysiology of prevalent human diseases, including cancer, diabetes, and atherosclerosis (1). Hence, uncovering mechanisms to suppress inflammation and enhance resolution is of immense interest (2-5). Resolution is orchestrated in part by specialized proresolving mediators (SPMs), including lipoxins, resolvins, protectins, and maresins (2), and by protein and peptide mediators (6). A common protective function of SPMs is their ability to limit excessive proinflammatory leukotriene formation without being immunosuppressive (2, 7). Specifically, resolvin D1 (RvD1) is protective in several disease models (8) and limits excessive leukotriene B 4 (LTB 4 ) production without compromising host defense (7, 9). However, the mechanism underlying these actions of RvD1 is not well understood.Arachidonic acid (AA) is first converted into 5-hydroperoxyeicosatetraenoicacid (5-HPETE) and then into leukotriene A 4 (LTA 4 ) by 5-lipoxygenase (5-LOX) (10, 11). Subsequent hydrolysis of LTA 4 by LTA 4 hydrolase yields LTB 4 (10, 11). During inflammation, 5-LOX is phosphorylated and translocates to the nuclear membrane, which favors the biosynthesis of LTB 4 (12-17). However, major gaps remain in our understanding of the relevance of this pathway to primary cells and animal models and how they are regulated by...

No abstract

BackgroundHuman Herpesvirus 8 (HHV8), the causative agent of Kaposi’s sarcoma, induces an intense modification of lipid metabolism and enhances the angiogenic process in endothelial cells. In the present study, neutral lipid (NL) metabolism and angiogenesis were investigated in HHV8-infected HUVEC cells. The viral replication phases were verified by rtPCR and also by K8.1 and LANA immunostaining.ResultsLipid droplets (Nile Red) were higher in all phases and NL staining (LipidTOX) combined with viral-antigen detection (immunofluorescence) demonstrated a NL content increase in infected cells. In particular, triglyceride synthesis increases in the lytic phase, whereas cholesteryl ester synthesis rises in the latent one. Moreover, the inhibition of cholesterol esterification reduces neo-tubule formation mainly in latently infected cells.ConclusionsWe suggest that a reprogramming of cholesteryl ester metabolism is involved in regulating neo-angiogenesis in HHV8-infected cells and plays a likely role in the high metastatic potential of derived-tumours.

Rationale: Glucagon is a key hormone that regulates the adaptive metabolic responses to fasting. In addition to maintaining glucose homeostasis, glucagon participates in the regulation of cholesterol metabolism, however, the molecular pathways underlying this effect are incompletely understood. Objective: We sought to determine the role of hepatic glucagon receptor (Gcgr) signaling in plasma cholesterol regulation and identify its underlying molecular mechanisms. Methods and Results: We show that Gcgr signaling plays an essential role in low-density lipoprotein (LDL) cholesterol homeostasis through regulating the proprotein convertase subtilisin/kexin type 9 (PCSK9) levels. Silencing of hepatic Gcgr or inhibition of glucagon action increased hepatic and plasma PCSK9 and resulted in lower LDL receptor protein and increased plasma LDL-cholesterol. Conversely, treatment of WT mice with glucagon lowered LDL-cholesterol levels, whereas this response was abrogated in Pcsk9−/− and Ldlr−/− mice. Our gain- and loss-of-function studies identified exchange protein activated by cAMP-2 (Epac2) and Ras-related protein-1 (Rap1) as the downstream mediators of glucagon’s action on PCSK9 homeostasis. Moreover, mechanistic studies revealed that glucagon affected the half-life of PCSK9 protein without changing the level of its mRNA, indicating that Gcgr signaling regulates PCSK9 degradation. Conclusions: These findings provide novel insights into the molecular interplay between hepatic glucagon signaling and lipid metabolism and describe a new post-transcriptional mechanism of PCSK9 regulation.